How NASA Uses Sapphires in Space

Precious gems with lofty ambitions.

NASA’s reputation suffered another blow Wednesday, as its Genesis spacecraft crashed into the Utah desert after a parachute failed to open. Hollywood stunt pilots had been hired to retrieve Genesis in midair, as researchers feared that a rough landing would shatter the capsule’s delicate cargo: disks of gold, sapphire, and diamond containing charged particles gleaned from the solar wind. Why construct the particle collectors from such precious materials?

Because, in addition to making jewelry sparkle, the gems and precious metals aboard Genesis have extremely low impurity levels. And that’s critical to the analysis of the solar wind, the particles of which contain infinitesimal traces of the 83 naturally occurring elements. If one of the collecting disks left Earth contaminated with even a tiny dollop of, say, magnesium, then researchers would be hard-pressed to know whether the sun was actually ejecting lots of the metallic element once the disk returned to the planet.

The Genesis capsule was outfitted with five collector arrays, each of which was tiled with 55 hexagonal wafers constructed of gold, sapphire, diamonds, and silicon. Two of the arrays were kept exposed nonstop throughout the three-year mission, while the three others were deployed only when specific solar-wind conditions required it—for example, when a coronal mass ejection resulted in the sun’s emission of an unusual number of particles.

Why all the different materials? Each gem or metal is uniquely adept at capturing a specific element. For example, pre-mission testing revealed that aluminum layered atop sapphire was perfect for collecting noble gases such as helium and neon, in large part because the mix responds well to a particle extraction technique known as laser ablation. Diamonds, meanwhile, are best for collecting oxygen, since they naturally contain so little of the common, life-giving element.

The most prevalent element in the wafers was silicon, which is why NASA was so concerned about preventing a crash. As the microchip industry knows well, silicon is invaluable because of its purity. But it’s also somewhat fragile, and a large jolt could shatter the collector arrays, leading to the contamination of the solar-wind samples that NASA spent approximately $260 million trying to gather. Unfortunately, that’s exactly what may have happened in the Utah desert today.

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